2015 Group Technical Report GR213 ELR 28161, ELR 28162

Abstract

Groote Eylandt is Aboriginal-owned land, as granted under the Aboriginal Land Rights (NT) Act 1976 (ALRA). The Groote Eylandt Mining Company Pty Ltd (GEMCO) has its obligations defined in various lease documents including Mineral Leases, Exploration Licences in Retention (ELRs) and Special Purpose Leases (SPLs), a Letter of Understanding dated 13 May 1965 and an Agreement dated 16 September 2006. Groote Eylandt is predominantly composed of a stable basement of Proterozoic quartz sandstones and quartzites. The overlying manganese deposits are part of a blanket of Cretaceous sediments lapping onto the western margin of the Proterozoic basement sandstones and quartzites of the McArthur Basin. The manganese orebody is a sedimentary layer, consisting of manganese strata occurring between clay and sand beds and gently undulates beneath the western plains of the island. It extends over an area of about 50 square kilometres as an almost continuous horizon ranging in thickness up to 11 metres. The ore body is thus essentially stratabound and strataform in character. This report covers what is commonly referred to as the 'Eastern Leases', the two Exploration Licences in Retention (ELR 28161 and 28162) east of the main mining leases. Granted in November 2010, these licences cover the areas previously held by GEMCO under Exploration Licence EL 10115 and 10108 respectively. A number of activities were conducted during the reporting period. Results from the 2013 drilling program were received and were used to update the geological model. During the 2014 drilling season, infill drilling continued to improve the confidence of the resource on the leases. A total of 707 Reverse Circulation (RC) holes were drilled totalling 16,001 metres with 7,275 samples collected. In addition, 10 diamond drillholes were drilled totalling 128.95m. The 41 samples collected were submitted for geometallurgical testing to update assumptions used in the resource model. Work continued on pre-feasibility and feasibility studies in which a further 23 mud rotary holes were drilled totalling 609 metres. The holes were established as groundwater monitoring bores and were installed in various areas of the leases. Ongoing cultural heritage and environmental studies were also initiated and are still currently in progress.